Knowledge of the genetic and molecular mechanisms by which the fate of retinal stem cells is determined will be necessary to manipulate the proliferation and differentiation potential of these cells for use in regeneration therapies to treat retinal diseases. We are focused on understanding the genes that control early commitment to neural and pigmented retinal identity with the intention of manipulating these genes to promote regeneration in the mammalian retina and to direct differentiation of specific cell types. Our work with the Rx homeobox gene demonstrates multiple roles for this transcription factor, ranging from initiation of optic vesicle formation, to determining neural retinal identity, and finally, to controlling growth and differentiation of retinal stem cells. [unreadable] [unreadable] Our long-term goal is to understand how proliferation and differentiation of the mammalian retina are regulated. In pursuit of this goal, the objective of this application is to investigate the role of the Rx gene in controlling the ability of a retinal stem cell to proliferate and differentiate. The central hypothesis of this proposal is that the Rx gene is necessary for determining and maintaining neural retinal cell identity and that it does so by promoting the proliferation of retinal stem cells at multiple stages during retinal development. [unreadable] [unreadable] The current proposal aims to continue our work on the Rx gene to understand its genetic and biochemical activities in early retinal development. The proposed work is designed in two Specific Aims: 1) to determine if Rx is both necessary and sufficient to specify neural retinal cell identity, using mouse transgenic and conditional deletion models of Rx gene function; and 2) to determine the role of the Rx gene in maintaining neural retinal progenitor proliferation. In this aim, conditional deletion of the Rx gene will be used to uncover its function in the optic cup. [unreadable] [unreadable] Collectively, these studies will yield important information that is necessary to manipulate endogenous retinal stem cells toward proliferation and ultimate use in restoring sight to the visually impaired. [unreadable] [unreadable]